Kenney W L, Ho C W
Noll Physiological Research Center, Pennsylvania State University, University Park 16802-6900, USA.
J Appl Physiol (1985). 1995 Oct;79(4):1112-9. doi: 10.1152/jappl.1995.79.4.1112.
During dynamic exercise in warm environments, requisite increases in skin and active muscle blood flows are supported by increasing cardiac output (Qc) and redistributing flow away from splanchnic and renal circulations. To examine the effect of age on these responses, six young (Y; 26 +/- 2 yr) and six older (O; 64 +/- 2 yr) men performed upright cycle exercise at 35 and 60% of peak O2 consumption (VO2peak) in 22 and 36 degrees C environments. To further isolate age, the two age groups were closely matched for VO2peak, weight, surface area, and body composition. Measurements included heart rate, Qc (CO2 rebreathing), skin blood flow (from increases in forearm blood flow (venous occlusion plethysmography), splanchnic blood flow (indocyanine green dilution), renal blood flow (p-amino-hippurate clearance), and plasma norepinephrine concentration. There were no significant age differences in Qc; however, in both environments the O group maintained Qc at a higher stroke volume and lower heart rate. At 60% VO2peak, forearm blood flow was significantly lower in the O subjects in each environment. Splanchnic blood flow fell (by 12-14% in both groups) at the lower intensity, then decreased to a greater extent at 60% VO2peak in Y than in O subjects (e.g., -45 +/- 2 vs. -33 +/- 3% for the hot environment, P < 0.01). Renal blood flow was lower at rest in the O group, remained relatively constant at 35% VO2peak, then decreased by 20-25% in both groups at 60% VO2peak. At 60% VO2peak, 27 and 37% more total blood flow was redistributed away from these two circulations in the Y than in the O group at 22 and 36 degrees, respectively. It was concluded that the greater increase in skin blood flow in Y subjects is partially supported by a greater redistribution of blood flow away from splanchnic and renal vascular beds.
在温暖环境中进行动态运动时，心输出量（Qc）增加以及血流从内脏和肾循环重新分配，从而支持皮肤和活动肌肉的血流按需增加。为研究年龄对这些反应的影响，6名年轻男性（Y组；26±2岁）和6名年长男性（O组；64±2岁）在22℃和36℃环境中，以峰值耗氧量（VO2peak）的35%和60%进行直立自行车运动。为进一步区分年龄因素，两组在VO2peak、体重、体表面积和身体组成方面进行了密切匹配。测量指标包括心率、Qc（二氧化碳重呼吸法）、皮肤血流量（通过前臂血流量增加来测定，采用静脉阻断体积描记法）、内脏血流量（吲哚菁绿稀释法）、肾血流量（对氨基马尿酸清除率）以及血浆去甲肾上腺素浓度。Qc在年龄组间无显著差异；然而，在两种环境中，O组均以较高的每搏输出量和较低的心率维持Qc。在60%VO2peak时，各环境下O组受试者的前臂血流量均显著较低。较低强度运动时，两组内脏血流量均下降（两组均下降12 - 14%），然后在60%VO2peak时，Y组受试者的内脏血流量下降幅度大于O组（例如，在热环境中分别为-45±2%和-33±3%，P<0.01）。O组静息时肾血流量较低，在35%VO2peak时保持相对稳定，然后在60%VO2peak时两组均下降20 - 25%。在60%VO2peak时，22℃和36℃环境下，Y组分别比O组多27%和37%的总血流量从这两个循环重新分配出去。得出的结论是，Y组受试者皮肤血流量的更大增加部分是由于从内脏和肾血管床重新分配的血流量更大。
